The story begins at IIM Ahmedabad, where Krish Malhotra is pursuing his MBA. Krish comes from a family very proud of their Punjabi heritage. He meets Ananya Swaminathan, who comes from a conservative Tamil Brahmin family. Krish and Ananya become friends and start studying together. Soon they begin dating, and stay together for their two years on the IIM campus. Krish confides in Ananya that his real passion is writing, which he wants to pursue a career in.
When their graduation comes, Krish and Ananya decide to get married. They introduce their parents to each other at the convocation ceremony. To their dismay, Krish's loud Punjabi mother Kavita does not get along with Ananya's reserved Tamilian parents Radha and Swaminathan. After graduation, Ananya begins her marketing job in her hometown Chennai and Krish goes back to his own hometown Delhi. Krish's brash family urges him to stay in Delhi and try to discourage him from his interest in writing. They also criticize his relationship with Ananya, and tell him to get an arranged marriage with a Punjabi girl. It is also evident that there is tension between Krish and his alcoholic father Vikram.
Krish leaves his dysfunctional family and starts a banking job in Chennai. During this time, he tries very hard to win over Ananya's family. He tutors her younger brother, gets her mother an opportunity to sing at an event for his workplace, and helps her father create his first PowerPoint presentation. After all his effort, Ananya's family agrees to the marriage with Krish. Krish and Ananya then travel to Delhi to win over Krish's family. Initially, Kavita and her family are hostile towards Ananya but come to like her after she saves Krish's cousin's wedding from being cancelled due to a dispute over dowry.
Krish and Ananya decide to take a vacation with their families before the wedding. The vacation does not go as planned when Kavita makes continuous snide remarks about Tamilian culture. Furthermore, Ananya and her parents overhear Krish falsely assuring his mother that she can treat Ananya however she wants after they are married. Having had enough of the insults, Ananya calls off the wedding and both return to their respective hometowns.
Krish and Ananya find it hard to live without each other. Sometime later, he gets a call from Ananya, who reveals that Krish's father had come down to Chennai to speak to her parents, apologizing for his wife's shallow behavior. This allows for Krish and Ananya to finally have their happy marriage, they became parents to twin boys and Krish publishes his book 2 States based on his and Ananya's life.